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Foreign Service

This month’s column is a mixed bag, with something for everyone: power supplies for oscilloscopes, brake-service tips and even a word-usage correction. The only thing missing is a good used car for your kid…

The first subject in our potpourri of topics this month is power options for digital storage oscilloscopes (DSOs). Now, some DSO batteries simply last longer than others. You may have tried to improve battery life by investing in an OEM battery and then fine-tuning the scope’s power-management settings. But in spite of these steps, the darn battery still might not have lasted as long as you hoped.

My field experience has been that the easier equipment was to operate, the more often techs would use it. Similarly, the longer a DSO’s battery life, the more likely techs were to use the scope. Unfortunately, some guys give up when a scope’s battery dies. They hate dragging an extension cord over to the vehicle and using the scope’s AC power adapter. Of course, the AC adapter is useless when a tech needs to scope something during a road test.

Furthermore, some techs I’ve met at my training seminars told me they’re buying their own scopes. They said their bosses won’t make the investment because they’re not convinced techs will use the equipment. (Sadly, sometimes that turns out to be true.) On one hand, a tech looking for a simple beginner’s scope may find some decent deals out there. On the other hand, issues such as short battery life and poor battery availability may turn a potentially good deal into a nightmare.

Even if battery life isn’t the issue, a simple accident could create the need for an alternative power supply for a DSO. A classic example occurred at my buddy’s shop. He upgraded from a fairly basic DSO to a very sophisticated model. The old scope was compact, easy to use and in excellent condition. Everyone at the shop agreed that it made more sense to keep it as a backup than to trade it in.

The techs used the old DSO to complement the new one—but then bad luck struck. The old scope happened to sit unused for about six months. The next time they tried to use it, it was dead. Not only did its batteries quit, but the cells also leaked severely and damaged the scope. Then they had no choice but to use AC power for this scope.

Several sources offer replacement DSO batteries. I’ll suggest two familiar, effective sources. The first is Automotive Electronics Services (www.aeswave.com). Its diagnostic equipment specialists may have an OEM and/or aftermarket battery for your DSO.

The other practical option may be the local Batteries Plus retail store (www.BatteriesPlus.com). Some techs I know had replacement battery packs custom built by this company. They were so pleased with the results that I did the same. To date, techs at Batteries Plus have built three DSO battery packs for me. In each case, they were able to recreate the battery pack with superior, modern AA batteries. (Not only do these batteries have considerably more capacity, they also don’t suffer from the “memory effect” that was common on earlier rechargeable batteries.) Batteries Plus also swapped over the wiring from the original battery assembly and shrink-wrapped the new battery pack so it looked and fit like OE.

A DC-to-DC converter is still another option for powering your DSO. One end of this converter plugs into a cigarette lighter socket or power port inside the car. The other end connects to your scope’s DC power port. This kind of converter allows you to shelve the scope’s AC adapter and bypass its battery or batteries.

There are a variety of these converters on the market. But my colleague and fellow columnist Mike Dale referred me to the Power Stream model shown on page 14 (www.PowerStream.com) for several reasons. First and foremost, the yellow adjuster on the face of the converter lets you choose one of seven different voltage outputs. Second, it includes six different output plugs; the output plug slides into the DC power port on your DSO. Third, these output plugs accommodate both types of terminal polarity (“center positive” or “center negative”). Therefore, the converter is more likely to match your DSO—not to mention other scopes and devices within the shop. I bought this unit online—about 30 bucks, including shipping.

This converter is protected by a 2-amp fuse hidden inside its cigarette lighter-shaped power plug. (Sure, real men don’t eat quiche and they don’t use fuses.) Like many other techs, I have an adapter with alligator clips on one end and a female cigarette lighter socket on the other. With this type of adapter, it’s a snap to connect a DC-to-DC converter directly to a vehicle’s battery.

The decal on the back of your scope’s AC adapter wall plug tells you its output voltage specification as well as the polarity of its center terminal. Common output voltages are 1.5, 3, 5, 6, 7.5, 9 or 12 volts.

Corolla Brakes Revisited

Back in the March 2012 issue, I described a contaminated master cylinder and an intermittent dragging brake condition it caused on a 2006 Corolla. That column prompted several responses from our eagle-eyed readers. First, I used the word hydroscopic to describe brake fluid’s tendency to absorb moisture. Vic Lucariello, among others, reminded me that the correct term is hygroscopic.

Meanwhile, readers Rick Rice and James Thornton emphasized brake hydraulic fundamentals in their comments. In fact, they argued that it doesn’t make sense not to open the bleeder fitting before pushing back a caliper piston. Gentlemen, I can’t agree more: Discharge that dirty, damp brake fluid right then and there through an open bleeder fitting.

Last but not least, I don’t recommend crimping or clamping any rubber brake hose any time for any reason. Thanks for your readership and we’ll look for you next time.